Local buckling design without effective width new developments in the building industry TRB - A2C06 Committee Meeting January 2004 Ben Schafer, Ph.D. The Johns Hopkins University

Profiles evolve – how does design keep up?

Direct Strength In the building industry we have recently added a new alternative method for local buckling design that: (1)requires no effective width calculation, and (2)incorporates a numerical analysis that accurately predicts local buckling even for complicated cross-sections.

Fictitious profile Examine bending Local buckling occurs at 0.75 of the reference bending load

Idea for incremental profile improvement Local buckling at 4 times referenceLocal buckling at 2.7 times reference Big boost from 0.75! I want to take advantage of that…. (1)hard to calculate by hand (2)effective width becomes overly complicated

Conventional approach Via a specification we get all local buckling modes, effective widths, effective properties, and finally the strength.

Direct Strength Approach Via alternative we get all local buckling modes calculated exactly, and the strength.

Direct Strength for Pipe… (could be strain based) M,T

Thrust - Columns Lipped channels Lipped zeds Lipped channels with int. web stiffener Hat sections Rack post sections 267 columns,  = 2.5,  = 0.84

Bending - Beams Lipped and plain channels Lipped zeds Hats with and without intermediate stiffener(s) in the flange Decks with and without intermediate stiffener(s) in the web and the flange 569 beams,  =2.5,  =0.9

DSM for flexible pipe? More research would be needed to bring the Direct Strength Method to flexible pipe, but the existing research plus the success of the AASHTO method demonstrate it is possible. Design for thin-walled flexible pipe has benefited from existing research, new design methods provide new opportunities for simplification and optimization.

CUFSM DSM Pipe